Method of making expandable rivets



1947. c. r. TORRESEN 2,426,422

METHOD OF MAKING EXPANDABLE RIVETS Filed Feb. 15, 1945 '2 sheds-sheet 2 Patented Aug. 26, 1947 UNITED STATES PATENT OFFICE METHOD OF MAKING EXPANDABLE RIVETS Carel T. Torresen, Santa Monica, Calif.

Application February 15, 1945, Serial No. 578,072

13 Claims.

The present invention relates to methods of making rivets of the expandable type and more particularly to hydrostatically expandable rivets and methods of making and installing such rivets.

In riveting and similar operations where it is required to fasten structural and other elements together, the arrangement of these elements frequently prevents access to the shank portion of the rivet which is required to be upset to complete the riveting operation. Such operations are commonly referred to as blind riveting and bolting and numerous expedients to accomplish these results have been suggested and used. In those cases Where bolts have been provided for installation from a single side of the work the results have been reasonably satisfactory, although where large and rapid production is required the expense and time involved makes their installation prohibitive. Since such types of blind fastening work, as met with in airplane manufacture, usually requires the use of blind rivets, several methods of-upsetting the rivet shanks have been proposed and used.

In certain of these prior rivet upsetting methods, the shank is tubular and is provided with a mandrel or wire having an enlarged portion which is drawn outwardly as the rivet is held in position thereby upsetting the inner shank portion, after which the mandrel or wire is either withdrawn or cut off and, where necessary, the hole in the rivet head sealed or closed. It has also been suggested to provide a chamber in the inner shank portion filled with an explosive charge which may be set off either by the application of heat or by percussion by striking a hammer pin Or other movable element from the head side of the rivet. Each of these types of blind riveting has, however, had certain deficiencies and objections and has not proven entirely satisfactory in production methods.

Th present invention relates to the method of making an improved expanded rivet of the blind type in which a recess or cavity is provided in the inner end of the shank and the shank portion upset or expanded by the application of hydrostatic pressure through a channel from the head of the rivet to the cavity, thereby completing the riveting operation. The pressure source may be either pneumatic or hydraulic and is subject to finer control and more uniform results than explosive rivets of known types. The invention also includes novel methods of manufacturin such blind rivets as well as the formation of such rivets with nibs or other means for the accommodation of the driving tool through which the hydrostatic pressure is applied. The present rivet is adapted to be manufactured from aluminum and aluminum alloys and other metals.

It is accordingly a principal object of the present invention to provide a method of making a hollow shank rivet of the blind type which may be expanded by the application of hydrostatic, pneumatic or hydraulic pressure. It is a further object to provide a method of makingan expandable rivet of a relatively safe and simple type as compared to other blind rivets of the tubular and explosive types, and of greater uniformity in final shape and strength. I

It is a further object to provide a method of manufacturing a hydrostaticall expandable rivet suitable for use as either a countersunk head, or exposed head type of any desired shape, and which may be installed either in work positions requiring blind riveting or where conventional rivets are used. It is a further object of the present invention to provide an improved method of manufacturing expandable rivets of both the countersunk or oval head type as well as an attached nib for the admission of the expanding fluid.

Other objects and advantages of the present invention will become apparent to those skilled in the art after a reading of the present description and the accompanying drawings forming a part hereof, in which:

Fig. 1 is a sectional view showing an early step in the manufacture of an expandable rivet to be provided with a nib projection;

Fig. 2 is a sectional view disclosing a further step in the manufacture of such a rivet;

Fig. 3 shows the same rivet completed and in position with the hydrostatic driving tool applied ready for expanding the same;

Fig. 4 is a partly sectioned view of the rivet of Fig. 3 after it has been expanded;

Fig. 5 is a sectional view of an early step in the forming of a countersunk head rivet with a protruding nib;

Fig. 6 discloses an intermediate operation in the forming of the'same nibbed countersunk head rivet;

Fig. '7 shows a later step in the manufacture of the rivet of Figs. 5 and 6;

Fig. 8 discloses an initial operation in the manufacture of a countersunk head expandable rivet without the nib;

Fig. 9 shows a sectional view of a further step in the formation of this rivet;

Fig. 10 is a sectional view of a still further stage in the formation of the same rivet;

Fig, 11 shows the ejection of the finished counter-sunk head nibless rivet shown in Figs. 8, 9 and 10;

Fig. 12 is a sectional view showing the method of converting a countersunk head to a button head; and

Fig. 13 is a sectional view showing the operation of swaging dies in the final stage of forming a nib on the rivet head.

Referring now to Fig. l, the numeral AI represents a cross section of a fixed die block having an enlarged cylindrical bore on the right side and a co-axial bore of lesser diameter at the opposite side. Both said cylindrical bores are concentric with each other and are joined by the tapered or chamfered portion at.JBC. A metallic billet of the desired material .and of .a predetermined volume is initially inserted into'the larger bore of the female die block'Al. This billet is preferably of a cylindrical shape with a slightly lesser diameter than the larger bore-of the die block and is inserted to aposition such as that occupied by the billet B6 in the die. block A shown in Fig.i8. The plunger El, of a diameter which closely fits the smaller bore of the die block, and having a cupped endEC, is locked in its predetermined position a shown in Fig. l. A male pressure die'or plunger DI provided with a cylindrical tongue portion DT and a recessed annular portion at Nl in its reduced diameter portion is then brought into position within the larger bore of the die block deformin the billet into the shape shown at El in Fig- 1. The rivet may be formed from a billet of either hot or cold material.

It will be noted from Fig. 1 that the tongue portion DT has formed an elongated cylindrical cavity CI in the rivet blank and the recessed an- "nular portionNl has assisted in forming a protrusion'on the head end of the rivet blank whichis subsequently to be formed into-the nib. A portion of the material of the initial billet has also been upset and forced into the restricted diameter portion of the die block to form the shank indicated at SI, being chamfered at its inner terminal by the cupped end EC of the rod E I. The volume of the initial billet is very closely predetermined for the particular size of the finished rivet and when the shouldered, portion of the pressure die DI reaches its final position as limited by contact with the face of the die block .Al, the material of the original billet has been completely upset and formed into the rivet blank The pressure die DI of Fig. 1. is then removed from the die block, the rivet blank BI i ejected by movement of the-plunger El; the blank may then be annealed and placed in the die block A2 shown in Fig. 2. This die block is similar in form and construction to Al :with the exception that the length of the larger diameter bore is not as great, and its plunger E2 is positioned at a predetermined distance from the face of the die block or other reference point such as the chamfered portion BC. With the mandrel rod R projecting a predetermined distance beyond the cupped end N2 of the pressure die D2, the latter is moved under pressure into the larger bore of the block, deforming and upsetting the rivet blank by forcing the mass of its material at the enlarged head portion inwardly both toward the end of the shank portion and centrally toward the axis of the rivet blank until it assumes the form shown at B2 in Fig. 2. The

rivet blank will now be seen to have its cavity reduced to a relatively small volume as shown at C2 and with lesser material forming the head portion beyond the extended shank diameter,

than in the blank Bl transverse shouldered portion BD in substitution for the tapered chamfer BC of the previously used die blocks. A cup-shaped pressure "maledieDdmoves into the die block upsetting the. rivet head to form an oval or button head as shown in Fig. 12. Thereafter, the blank is transferred to a holding die block Al. The shoulder of the blank is held against the die block by a plunger-D9 while a pair of oppositely moving swagingdies F3 and F4 are brought together .to form the. necked-down portion NN, resulting in the finished rivet of Fig. 3. The'mandrel rod R is then removed from the blank which is ejected from the die block by movement of the plunger Em and the formed blank then annealed or heattreated in the case of certain alloys, tumbled and preferably given an Alumilite or equivalent ano-dic treatment to finish the. expandable rivet which is then ready for use.

'When it is desired to manufacture an expandable rivet oi the countersunk head type provided with an external nib on theflat head, the above described steps-as shown in Figs. 1 and 2 are supplemented by the-insertion of the rivet blank B2 of. Fig. 2 into a die block A las shown in Fig. 7. Thefac-e of the latter die block is flush with the face of the finished rivet head HK and the plunger rod E5 is broughtup to its predetermined position, at which it backs up the shank of the rivet blank, and is locked at this position. Oppositely moving swaging dies Fl and F2, having their working surfaces curved to form the neck portion of thenibprojection, are then brought together as shownin Fig. '7. Simultaneously the pressure plungendie D5, suitably apertured for the .mandrel rod R,.is brought in an axial direction against thc.outer end of the projecting nib portion N4. The result of these operations is to deform the partly finished nib N2 of the rivet blank B2 shown in Fig. 2, into the finished nib. shape N4 of Fig. '7 similar to the elliptical or lentil-shaped nib N shown enlarged on the rivet head of Fig. 4.

Theapplication of the oval head expandable rivet, formed by the above described process of Figs. 1 and 2, is shown in Figs. 3 and 4. The above referred. to fiat head rivet, as finally formed in Fig. '7, is expanded or applied in substantially the same manner. Reference toFig. 3 shows the finished ovalor button-head 1-113 of the rivet l2, the shank S of which is chamfered at its inner end at SC and provided with the cavity C, which communicates -with the nib N by means of the air. passage or tube T. Thefinished rivet has been positioned within the aligned aperturesof the usual diameter providing suitable clearance in the two worksheets or plates WI and W2 which it is desiredbe fastened together. A driving tool P havin -a recessed concave end portion PN of a shape to closely engage the nib N of the rivet is then positioned by a lateral movement upon the nib, bearing against the rubber gasket G in the recessed head of the driving tool. The pressuredriving tool P is also provided with an axial cavity PT which becomes aligned with the air passage T through the axis of the rivet. A hydrostatic pressure source communicates with the chamber PT in the drive tool and, while the tool is pressed firmly against the outer surface of the nib N causing the head HB of the rivet to closely bear against the outer surface of the work plate W2, the pressure is released into the comm-unicating passages PT and T by the opening of suitable Valve means. This fluid under hydrostatic pressure passes through the aligned passages into the cavity 0, being confined by the gasket G, and the pressure of the tool applied against the nib, from leaking out around past the nib'N.

When a predetermined hydrostatic pressure has been applied within the cavity C of the rivet I2 of Fig. 3, the walls of the rivet shank become deformed and upset into the shape shown for the rivet l3 in Fig. 4. Since the internal pressure within the original cavity is exerted equally in all directions, a shank wall of uniform thickness would result in substantially a spherical form. However, the amount of material at the shank end is considerably greater than that in the walls adjacent the cavity, with the result that the upset shank takes an oblate globose shape having its major axis transverse to that of the rivet, such that the shank wall is upset into the form shown in Fig. 4 and the referred to flattening of the chamber is caused by the greater lateral deformation due to the exertion of the internal pressure in a radially outward direction from the axis of the rivet which has the effect of drawing the shank end SC slightly toward the worksheets Wi and W2. This serves to draw the sheets tightly together with the pressure being exerted mainly around the edge of the hole in the sheet WI at the intersection of the shank portion with the upset flattened spherical portion SU.

The pressure driving tool P is then removed laterally from the nib N of the driven rivet and the structural application of the rivet has been completed. In many installations it is not necessary that the nib N be removed from the rivet head. In exposed surfaces such as are commonly found in airplane construction for aerodynamic and other reasons it is desirable that the tip be broken off or removed and that a rivet of the dimpled or countersunk type be used in order to provide a substantially flush outer surface with the worksheet W2. Where necessary the nib may be broken off at the neck by a light blow of a hammer, snipped by a pair of cutting pliers or broken by the removal of the driving tool.

Such countersunk head rivets can be satisfactorily applied either with or without a nib of the type described above. A nibbed or tipped flat countersunk head rivet is preferably formed as shown in Figs. 5, 6 and 7. Referring now to Fig. 5, a cylindrical billet, preferably hot, of the proper volume is inserted in the die block A3, after the plunger E3 is predeterminedly positioned with respect to a reference point on the die block. A male pressure die D3, having a tongue portion DT, is then moved into the larger bore of the die block upsetting and deforming the billet material into the shape of the die blank B3 shown in Fig, 5. As the pressure die is removed a cavity C3 is formed within the die blank and a chamfered shank end formed corresponding to the cupped end EC of the plunger rod E3. After ejection by the rod E3 the blank is annealed and reinserted in the die block A3, or the intermediate annealing step may be omitted in the event the operations can follow in sufficiently rapid succession. The plunger rod E3 has in the mean-- time been withdrawn to the predetermined posi tion indicated at E4 in Fig. 6, and a cupped male pressure die D4 is inserted together with its mandrel rod R projecting beyond the die end a predetermined distance. Accordingly, as the rivet blank B3 is positioned in the die block with the plunger D4 the mass of material in the adjacent larger end of the blank will be extruded or forced into the shank portion indicated at $4. This operation reduces the volume of the cavity to that indicated by the dotted lines at C4 and the material closely encloses the mandrel rod R to form the passageway indicated by the dotted lines at T2. The remaining mass of the material in the adjacent end of the blank is upset and formed into the flat countersunk head portion HK and the protruding nib portion N3.

The rivet blank as shaped at B4 in Fig. 6 is then removed from the die block A3 by the ejecting action of the rod E4 and is placed in a die block A4 as shown in Fig. 7. The face of the latter die block, as described above, is flush with the face of the countersunk rivet head HK and the plunger rod E5 is brought up to a predetermined position where it backs up the shank of the rivet blank. As the blank has been brought from the previous operation the nib N3 is of an outwardly diminishing shape of gradually reducing circular cross section. This nib N3 is the only portion of the head of the rivet blank which projects beyond the face of the die block A4 or the countersunk surface of the head I-IK. Oppositely moving swaging dies Fl and F2, having their working surfaces curved to form the neck portion of the nib projection are then brought together as shown in Fig. 7. At the same time a pressure plunger die D5, suitably apertured for the mandrel rod R, is brought in an axial direction against the outer end of the projecting nib portion,

The result of these operations is to deform the partly finished nib N3 into the finished nib shape N4 of Fig. 7, similar to the nib N shown enlarged on the oval head rivet in Fig. 4. The rivet blank is then ejected from the die block A4 by Withdrawal of the plunger die D5 and th mandrel rod R, as well as the laterally or vertically opening swaging dies F! and F2, after which the blank is ejected by movement of the plunger E5. The rivet blank is then heat-treated and finished by the tumbling and Alumilite anodizing steps referred to in connection with the oval head rivet. The fiat countersunk head nibbed rivets are applied or upset in substantially the same manner as the method described above for Figs. 3 and 4.

Figs. 8 to 11 inclusive disclose the major steps in the manufacture of a flat countersunk head rivet of the nibless type also expandable by pneumatic or hydraulic pressure as in the case of the above described rivets. The plunger E6 is inserted in the die block A5 to the predetermined position indicated in Fig, 8, the plunger having a cupped end as at EC. After the plunger is locked in this predetermined position, a hot cylindrical billet B6 of the proper material, temperature and volume is inserted in the larger bore of the female die block A5 as shown in this figure. A pressure plunger D3 having a shouldered intermediate portion DI, as well as a rounded cylindrical tongue portion DT is inserted in the larger bore of the die block A5 and the pressure applied until the shoulder bears against the face of the die block and the original hot billet i de- 7 'formed into therivet-bla'nk B1, havinga c'en- 'tral cavityC'L as indicated in'FigZQ. The -plunger D6 is then removedand the opposite' ejecting plunger moved back to a predetermined position indicated at E8 in Fig. 10, where it is again locked.

A male pressure die Dl, provided with a mandrel rod R and a reduced diameter'head-forming end portion DH, is then brought intothe larger bore of the die block and the pressure ap- 'plied. In forming the communicating passageway-T8 as the plunger D! is inserted in the die block prior tothe' relative'position shown in Fig. 10, sufficient pressure is applied to it to'extrude the material from the rivet blank Bl around the mandrel rod R, whichis of suffi'cientlength to touch ornearl touch the bottom of the hollow chamber C8, asshown in'this-figure. As the pressure is applied to the rivet blank material by further movement of the'plunger portion DH,

which is integral with the main portion DI, the.

mandrel rod R is preferably inserted at a slightly greater speed than the plunger DH such that it preferably protrudes into the hollow cavity C and does not allow the metal to swell sufficiently to stick to the mandrel rod. When the plunger die D1 reaches its terminal position the rivet blank is deformed as at B8, with the final shaped cavity C8, the shank portion S8 and the central communicating passageway formed at T8 by the needle rod R. The pressure die D! together with 1 its mandrel rod R is withdrawn from the die block and the rivet blank B8 permitting theejecting plunger to'be unlocked and movedinto its for- *wardposition shown at'EB in FigJ-ll, thereby ejecting the completely formed rivet it as shown in this figure. The rivet .l is provided with a fiat countersunk head HK, the cavity Ccommunieating with the outer face of the head by means of the tube T running co-axially within the shank S. The rivet can then be prepared and finished by the above mentioned heat-treating, tumbling and Alumilite anodizing steps.

The countersunk head nibless rivet is applied by a'different tool, not shown, than that shown for the nibbed rivet in Fig. 3. The rivet gun for this flat head type is preferably provided with a pair of hinged gripping-elements, the grip on the rivet head edges being released as the endof the rivet gun is pressed against the rivet head-and an.

intermediate rubber sealing gasket. Pullin of the gun trigger permits hydraulic pressure to be exerted against and into the passage T, forcing the rivet against the workplate and-after entering the passa'geexpanding the same in the cavity C in a manner similar to that shown in Fig. 4.

It will be apparent that not all of the opera tions described above need be performed in the same die block. It may be advisab-le in sorneinstances to use separate, integral'die blocks of predetermined dimensions for each stage in the formation of the rivets in order to obtain maximum production. It is also possible to form the reduced diameter passageway without the use of mandrel rod R, but it is desirable to retain it if a very smooth and uniform passageway is required.

Other modifications and advantages of the present invention both with respect to general arrangement and detailed features which may become apparent to those skilled in the art after a reading of the foregoing specification are each intended to be embraced within the scope and spir it of this invention as more particularly defined-in the appended claims.

I claim:

-1. The method of making an expandable rivet 1 including the insertion of a cylindrical metalbil- -let within an orificed die block,'the positioning of a shank length determining plunger with rea central cavity, the insertion of a mandrel rod of less diameter than said tongue portion within said cavity and the extrusion of the billet material'from said head portion around a portion of said mandrel rod into said shankportion, the withdrawal of said mandrel rod from said rivet blank and the ejection of said blank from said die' block.

2. The method ofmaking an expandable rivet including the insertion of a cylindrical metal billet within an orificed die block, the positioning of a shank length determining plunger with respect to said block, the insertionof a pressure die having an orifice-forming tongue portion within said die block, the deformation of said billet into head and shank portionspierced by a central cavity extending to near proximity to said shank length determining plunger, the insertion of a mandrel rod of less diameter than said tongue portion within said cavity and the extrusion of the billet material from said head portion'around a portion of said mandrel rod into said shank portion, the withdrawal of said mandrel rod from said rivet blank and the ejection of said blankfrom said die block.

3. The method of making an expandable rivet ing an orifice-forming tongue portion within said die block, the deformation of said billet into head and shank portions pierced by a central cavity extending to .near proximityv to said shank length determining plunger, the insertion of a mandrel rod of less diameter thansaid tongue portion within said cavity and the extrusion of the billet .material from said head portion around a portion .of said mandrel rod into said shank portion to form a passagewayof reduced diameter for a predetermined length of shank, the withdrawal of said mandrel rod from said blank and the election of said blank from said die block.

=4. The method of making an expandable rivet including the insertion of a cylindrical metal billet within an orificed die block, the positioning'of a shank length determining plunger with respect to said block, the insertionof a pressure die having an orifice-forming tongue portion within said die block, the deformation of said billet in head and shank portions pierced by a central cavityextending to near-proximity -to said-shank length determining plunger, the extrusion of the billet material from said head portion tocomplete-said head and to form an-adjacent shank portion of predetermined length incorporating an orifice 9 orifice cavity into said blank orifice cavity and the extrusion of the blank material from said head portion around a portion of said mandrel rod into said shank portion adjacent said head portion, the withdrawal of said mandrel rod from said rivetblank, and the ejection of said blank from said die block,

6. The method of making an expandable rivet including the insertion of a blank, preformed to include a partially formed head and a shank portion and incorporating an Orifice cavity throughout most of its length extending inwardly from said head, within an orificed die block, the insertion of a pressure die into said orificed die block and the extrusion of the blank material from said head portion into an extension of said shank portion, simultaneously nearly closing said cavity orifice in said extension of said shank, the withdrawal of said pressure die, and the ejection of said blank from said orificed die block.

7. The method of making an expandable rivet including the steps of deforming a metal billet to provide a partially formed head portion and a first shank portion, both of circular cross section; forming a central cavity of relatively large diameter extending entirely through said head portion and through the major part of said first shank portion; and reducing the diameter of a part of said head portion to correspond to that of said first shank portion and to form a second shank portion in continuation thereof, simultaneously reducing substantially the diameter of said central cavity throughout said second shank portion.

8. The method of making an expandible rivet including the steps of: deforming a metal billet to provide a partially formed head portion and a first shank portion, both of circular cross section; forming a central cavity of relatively large diameter extending entirely through said head portion and through the major part of said first shank portion; and reducing the diameter of a part of said head portion-to correspond to that of said first shank portion and to form a second shank portion in continuation thereof, simultaneously reducing substantially the diameter of said central cavity throughout said second shank portion and the remaining head portion.

9. The method of making an expandable rivet as set forth in claim 7, including the further step of inserting a mandrel rod in said cavity to limit and control its reduction in diameter during the formation of said second shank portion.

10. The method of making an expandable rivet as set forth in claim 8, including the further step of inserting a, mandrel rod in said cavity to limit and control its reduction in diameter during the formation of said second shank portion.

11. The method of making an expandable rivet including the steps of: deforming a metal billet to provide a partially formed head portion with a first shank portion extending axially therefrom in one direction and a boss extending axially therefrom in the opposite direction; forming a central cavity of relatively large diameter extending entirely through said boss and head portion and through the major part of said first shank portion; extruding a part of said head portion to form a second shank portion in continuation of said first shank portion without substantially modifying said boss, and simultaneously reducing the diameter of said central cavity throughout the length of the second shank portion and the remaining head portion; and necking down said boss to provide a tool attaching nib.

12. The method of making an expandable rivet including the steps of: providing a die block with concentric bores of different diameters; placing in the larger bore a cylindrical metal billet of corresponding diameter; forcing an orifice forming tongue portion axially into said billet and applying axial force to said billet to simultaneously extrude a portion of said billet into the smaller bore and to form a central cavity therein extending through the major portion of its length; removing said tongue'portion and extruding an additional portion of said billet into said smaller bore to form a complete rivet shank, simultaneously reducing the diameter of part of said central cavity; and ejecting said finished rivet from said die block.

13. The method of making an expandable rivet as set forth in claim 12, including the further step of inserting a mandrel rod of reduced size in said cavity during said second extruding operation to limit and control the reduction in diameter of said cavity.

CAREL T. TORRESEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,281,930 Flannery et al Oct. 15, 1918 2,128,705 Hatebur Aug. 30, 193 8 2,331,324 Jakosk Oct. 12, 1943 

